Fluid pressure system



How 11, 1941. c. I. MacNEIL 2,262,331

FLU-I'D rnmssunn SYSTEM I 2 Filed Dec. 5, 1940 2 Sheets-Sheet 1 INVENTOR. Char/es 1. Mac /Ve/'/ Patented Nov. 11, 1941 UNITED v STATE Charles 1. Mail, Glen mi, N. 1., assignor to Bendix Aviation Corporation. South Bend, 1116., a corporation of Delaware Application December 5, 1940, Serial 1%. 368,721

1 Claim.

This invention relatesto fluid pressure systems, and particularly to pumping, mechanism for. maintenance of an ad quate sup ly of'fluid under pressure throughout the period vof operation of anyxsystem with whichisaid pumping mechanism is employed. i i i In the drawings the invention is shown applied to the maintenanceof-proper ail-pressure within a sealed "cabin orcompartment :of an aircraft; also to the maintenance ofa' supply Of fluid pressure for operation of .thefair supplying means, as well as for operation -of other a-fluid pressure responsive means performing various services incidental' to-the flight titan-aircraft, as for example, pumps and fluid motors controlling the operationof airfoil surfaces, flight directional dedevices, flaps, brakes, doors, undercarriage assemblies, propeller pitchcontrols, and superchargers. i I e r A system of the character indicated is preferably provided with :interlockingmeans between the elements of tthefisy'stem .which control "the supply of breathable to'the'aircraft cabinet compartment,- in which the passengers crew are confined on the one'ihand, andlthose elements of the systemwhich control, the performance of the various services fheretofore mentioned, on

the other; the-eifect beinggsuchas toassureequal- Q ization'of 'loads transfer-of energy. from any part of thesystem to anyiother'flpart whenever. suchttransferdesirable for ztheymainte- An object a of the invention isto' provide pumpmg mechanism pfsn h mn gm m andzchm teristics as' jto facilitate attainment of th r u t J'ustdescribeda in excess of that heretofore employed in variable volume pumps. H

These and other objects become apparent from. inspection of the following specification when read withreference to} the accompanying drawings wherein is illustrated the preferred embodiment of the invention. Itis'to be expressly motored aircraft having a sealed cabin whose air content is' to be varied as desired, and also including flight controls of diverse kinds, operable by fluid stored under pressure in an accumulator whose feed circuit is interlocked .with the feed circuit of a fluid motor constituting the energizing meansfor the cabin air supplying pump (hereinafter referred to as a supercharger); the two feed circuits being subjected to common barometric control-means in such manner as to insure smooth, uninterrupted and properly proportioned delivery of power to all work performing elements, regardless of disturbances or failures that may occur from time to time at one or more of the pressure generating sources.

(Thus the feed circuits constitute one major phase of the system, while the common barometric control means constitutes a complementary and co-ordinate phase of the system.)

Fig. 2 is a longitudinal sectional view of one :of the pressure generating sources; such pressure generating source, as illustrated, being in the nature of a variable delivery pump of novel construction, driven directly from, and by, one of the four propeller driving motors of the craft;

there being, in the preferredembodiment, one such variable delivery pump for each motor, and

, finance of the predetermined pressure-conditions.

understood, however, that the drawings are for the purpose of illustration only, and are not'designed as a definition of the limitsof the invention, reference being had to the appended claim for this purpose;

In the drawings: a Fig. 1 is a schematic view indicating the preseparate drives from each motor to the particular pump associated therewith.

Fig. 3 is a transverse sectional view along line 3-4 of Fig. 2.

In Fig. 1 the invention is shown applied to an aircraft having .a sealed compartment HI, and suitable for sub-stratosphere flight under the propelling power of its four engines ll, l2, l3 and I4, adapted to drive propellers I6, l1, .l8 and I 8, respectively,and also provided with power take-oil's to energize the pumps 2|, 22, 23 and 24, respectively, constituting (with supplementary pumps 2m and 22a driven from engines II and I2, respectively) the pressure generating sources of the system. The internal construction of pump 24 is shown in Figs. 2 and 3, and the internal construction of each of the other three pumps 2|, 22 and 23 is preferably identical with that of pump 24. The latter will be described more fully hereinafter.

ferred mode of applying the invention to a fourinterconnected, or if separate, there may be a corresponding duplication of parts, etc., for each.

Broadly, the compartment represents any part or all of the cabin or body of the craft which may be adapted to retain air at suitable pressure, for the purposes of the invention.

Considering the single compartment shown (which may be identified as a pressure compartment) it is intended to enclose and retain air at a pressure greater than outside pressure, from the lowest altitude at which reduced airpressure tends to discomfort, injure or disable occupants of an aircraft, up to any practical maximum altitude. The compartment I has any desired structural features enabling it to retain the desired pressure, while serving other necessary purposes. It is, however, here remarked, that the pressure to be maintained within the compartment need never be, for present purposes, greater than 15 lbs. per sq. in., and there will always be an external, partially balancing pressure, which of course decreases with altitude. The internal pressure may in fact, in many cases, be somewhat less than 15 lbs. without serious discomfort.

For supplying and/or maintaining air at a desired pressure in the compartment, in the preferred embodiment of the invention, a pump or compressor 3| is provided; the said pump 35 (hereinafter referred to as the supercharger) being mechanically driven by a fluid motor 32 to which fluid under pressure is supplied at such rates and pressures as are determined by the action of the barometric control unit 33 and the circuit 34 associated therewith. This circuit 39, as indicated particularly at 33a and 39b, feeds directly to pumps 2i and 22 and acts through servo-motors 33 and 31 (associated with pumps II and 22, respectively) to control the output of said pumps; and said circuit 33, also acts, indirectly, upon the other two pumps 23 and 20, as will be further explained.

The manner in which servo-motors 33, 31, 38 and 39 control the output of the associated pumps Ii, 22, 23 and 24, respectively, will be explained by referring to Figs. 2 and 3, wherein the pump 24 (typical of pumps H to 24, inclusive) is shown sectioned along intersecting planes. Pump 24 is represented in these views as having a series of abutting casing sections, including a head section II, a base 82, (omitted in Fig. 2) and intermediate sections 83 and 84, the section 83 being the gear containing section, and being abutted on the top by flange 86 of head section 8!; while section 84 is abutted on the bottom by the base 82. Through these sections extends the engine driven actuating shaft 89 carrying pump gear II which meshes with gear 92 (not shown in Fig. 2, but see Fig. 1) to produce the pumping action. A set of idler gears 93, 96 mesh with gears ll, 92, respectively, on the suction side of the pump, and are adapted to slide, from time to time, along the tooth faces, thus varying the extent of inter-engagement therebetween and thereby altering the volume of pumping space and hence the output at delivery port 96.

The means for controlling the sliding of idler gears 93;, 94 along the faces of the teeth of gears I 92, respectively, is shown as including a threeway slide valve IOI with a hydraulically unbalanoed plunger, hollow-bored to accept a compensiting spring I 92. A port I03 normally connects the m'essureside of the pump to the space between land?! and I0! of the valve IOI, the land I06 beiiiz 'of slightly larger diameter than land I01,

while land I01 operates in the smaller bore I09. When the valve IN is shifted to the left from the position indicated in Fig. 3 communication is established for delivery of fluid to a cylinder 39, the delivery being from the supply passage I03 to the annular chamber in bore I09 between the lands I0! and III, and from said chamber to the cylinder 39 by way of the intervening passages H4, H6 and Ill, as shown in Fig. 2, the longitudinal passage II'I terminating in a radial port I20 which feeds into the annular space bewith the teeth of the gear 9|.

an operating in the slightly larger bore I08,

tween the piston rod I22 of the piston I2I and the cylinder 39 in which said piston fits as shown in Fig. 2; the piston I2I, with its rod I22, being held stationary in the position to which it is adjusted by the adjusting means I26, and the cylinder 39 being slidable with respect to said piston I2i in response to the admission of fluid by way of the ports II! and I20 above described, and such sliding of the piston 39 being yieldably opposed by the compression spring I25, one end of which abuts the piston I2I and the opposite end of which is seated in the end of the bore of the assembly which includes the cylinder 39 and the idler gear 93 previously described; it being understood that there is a second cylinder (I39) corresponding to the cylinder 39 and having the idler gear 94 integral therewith, a second passage (2II) corresponding to the passage Ill; and a second piston rod (222) corresponding to the piston rod I22. Passages 38 and I38 relieve the spaces to the left of cylinders 39 and I39, respectively, of any vacuum caused therein by movement of said cylinders in their respective bores.

When fluid is admitted to the cylinder 39 the pressure thereof against the portion I29 of said cylinder causes the assembly 39, 93 to move to the left as viewed in Fig. 2, thereby moving the gear 93 into a condition of mor complete engagement with the teeth of the pumping gear 9|. This correspondingly decreases the volume of fluid delivery and hence decreases the pumping action. The resulting decrease in pressure at the discharge passage 96 of the pump causes a corresponding pressure decrease in the port I03, and this decreased pressure acting against the land I01, is insuflicient to balance the opposite action of the spring I02. The latter therefore returns the valve IN to the right, that is, back to the position indicated in Fig. 3, thereby reestablishing communication between the passages II'I, H6 and H4 on the one hand, and the discharge passage 1 I2 on the other; said passage II2 being located between the lands I01 and III of the valve IOI as shown in Fig. 3. As shown in Fig. 2, this discharge passage I I2 communicates with the bore I I5 of the pump shaft 89 and from passage H5 there is a port I30 by which the fluid is allowed to drain back to the suction side of th pump, and thence to a suitable reservoir which may be the sump indicated at 50 in Fig. 1. The resulting loss of fluid from the cylinder 39 allows spring I25 to expand, thereby shifting the cylinder 39 to the right again and tending to restore it to the position indicated in Fig. 2, in which position the pumping action is increased by reason of the sliding of the gear 93 toward a position of minimum inter-engagement This cycle of action thus varies thepump delivery rate in accordance with output pressure, and tends to reduce the delivery toward the zero point whenever the pump delivery is being transferred from one outlet to another in the manner hereinafter described.

Referring again to Fig. 1, the accumulator 4|, adapted to supply fluid under pressure, as needed, for actuation of the various flight control units of the craft, is fed by a supply line 42 leading thereto from control valve 43, the latter being supplied with fluid directly from pump 24, by way of line 44, in which is preferably included a check, or non-return, valve 43. Control valve 43 is so constructed that when the accumulator 4| receives its full charge-say, 1400 lbs. per sq.

in.-the flow from pump 24 is shunted into the feed line 43 leading to the fluid motor32; but just before this shunting occurs, the pressure rise in line 44--that is, at the delivery side 33 of pump 24-operates to reduce the output of this pump 24 to a point approaching zero; the manner in which this output reduction is effected having been described above with particular reference to Figs. ,2 and 3 wherein the operating parts of said pump 24 are shown in detail. As a consequence of this reduction in output prior to transfer to circuit 43,- there is an absence of sudden shock upon the system, and the absorption of the additional pressure source for circuit 43 is allowed to proceed gradually, so that there is a smooth "leveling action as between all four pumps, all of which'have delivery lines capable of feeding the line 43 supplying the fluid motor 32.

In addition to feeding the line 43, pump .24 simultaneously becomes interlocked with the other pump as a feeding means for the barometric control circuit 34, 35. This interlocking of pump 24 with the other three pumps (the latter being operative upon the barometric control circuit theretofore) is brought about by reason of the shunt circuit 5| from motor feedcircuit 43 to a two-way valve 52 with a flow restriction oriflce 53 and an annular chamber 34 shiftableto connect barometric control circuit lead 56 to conduit '55 and thus to the. discharge pipe 51 passing from pump 24 to pump 23 and includ-' ing a non-return valve 33.

As previously noted, pump 23, like pumps 2|, 22 and 24, has a two-stage servo-motor 33 associated therewith; it being understood that-the servo-motors showndiagrammatically at 33, .31, 33 and 33 in- Fig. 1 are-actually built into the pump 2|, 22, 23 and 24, respectively, and have an actual appearance corresponding to that shown at 33 (pump 24) in Figs. 2 and 3, and

- heretofore described in detail.

Pump 2: also has communication with a bypass valve 32, and the normal path of flow therethrough is by way of annular chamber 33 which normally connects line 34, 33 with the line 31 leading to the fluid motor feed line 43; but whenever pump 24 ceases to function, the pressure from pump 23 exerted against the smaller piston 33 (by way of lines 64 and 1|) exceeds the pressure acting oppositely upon the larger piston 65 and thereby shuts oil? flow through chamber 33 and diverts the flow to the accumulator control valve 43 and thence to the accumulator, the new path being by way of leads 64, longitudinal grooves 13, passages 12, 13, 44 and 42. Included in said new path is a tap-off 13 leading to one end of a two-way valve 11 (similar to valve 52) and the pressure thus exerted on said valve 11 operates to interrupt the flow previously maintained through annular chamber 13 of said valve, as the connecting link between barometric control lines 34 and 340, on the one hand, and line 13 of pump 23 on the other.

The flow from pump 23 to accumulator 4|, by

the circuit above traced, continues until such time as the predetermined maximum pressure is attained, whereupon the two-stage servo-motor 33 reduces the pump 23 delivery to nearly zero, and the line 33, 31 is thereby re-opened, thus augmenting the supply to supercharger driving motor 32; the action of servo-motor 33 being i such as to permit the gradual leveling of the load, as heretofore explained in connection with the description of the operation of servo-motor 33 of pump 24.

Thus there is an alternate cutting invand out of this additional pressure source and a consequent control of the fluid supply not only to the feed lines 43 for the supercharger motor 32 but also to the barometricaily controlled circuits 34a, 34b-and 34c supplementing thesupply from source 53 to the pumps 2|, 22 and 23; such control action being in turn influenced by the concurrently eil'ective barometric control constituted by the shiftable valve 33 which responds to every change in the pressure differential between the pressure within the cabin III on the one hand, and the external atmospheric pres sure on theother; it being understood that the lefthand side of the barometric unit 339. is open to the atmospheric outside cabin l0 while the righthand end of unit 33a reflects the pressure within the cabin Ill due tothe connection indicated at 33!).

The supplementary pressure generators 2|a and 22a are desirable as a means of assuring delivery of fluid to the unit 33 from the source 53 regardless of the positions of the gears of the pumps'2l to 24 which are controlled by the movements of the servo-motors 33 to 33, respectively, wherefore there is assurance that unit 33 will always receive a sufficient supply of fluid to take care of all requirements, as for example,

,tion of the pumps 2| to 24, inclusive, of which the pump 24 as shown in section in Figs. 2 and 3 is representative, it will be noted that the only gears which move axially are the idlergears 33 and 34. The actual working gears 3| and 32 (with which the idler gears 33 and 34, respectively, mesh) have permanently fixed axial positions, in that they completely flll the space between the conflning elements 34 and 33 (Fig.

.2). Thusthe working faces of the pump are of constant area, although the actual volume of the pumping space varies in accordance with the axial shifting of the idler gears 33 and 34. This mode of controlling the output differs from that of certain prior art constructions wherein the actual area of the engaging surfaces of the working gears is caused to vary as the means of reducing or increasing the pumping action in accordance with pressure variations. By resorting to the use of idler gears and causing said idler gears to shift their positions in relation to the working gears I achieve results equivalent to those of the prior art but without the necessity of shifting the relative axial positions of the working (pumping) gears themselves. What is claimed is: x

In a pump having a pair of working gears and a pair of idler gears, there being one idler gear in partial mesh with each working gear when the developed pressure is low, means for holding said working gears in fully meshed relationship, one to the other, at all pressures developed by the pump, an inlet port to direct fluid into the space between said two working gears, an outlet port to receive the fluid delivered thereto by the rotation of said working gears, means for retating said working gears and thereby creating a pressure at said outlet port, and means responsive to an increase in such pressure to move said idler gears into a condition of more complete mesh with their respective working gears engaged therewith, wherefore the free space remaining for fluid flow through the pump is diminished, and the delivery volume per revolution of said gears is correspondingly reduced. CHARLES I. MACNEIL. 

